The present invention relates to an expansion card interface according to the preamble of claim 1, electronic device according to the preamble of claim 10, and expansion card according to the preamble of claim 19.
A PCMCIA interface (Personal Computer Memory Card International Association) is one known interface which is used in connection with electronic devices to connect expansion cards, such as memory cards (for example flash memory cards), wired line modems and various kinds of input/output cards (I/O), to an electronic device. Such electronic devices and PCMCIA cards include connectors according to PCMCIA standard, for example such that the connector of electronic device is a so-called male connector (connector with contact pins), and the connector of the interface card is a so-called female connector (connector with jointing sleeves). Thus, an electrical contact is formed between each contact pin and the corresponding jointing sleeve when the interface card is connected to the connector of the electronic device. The PCMCIA standard defines the normal function of each contact pin and each jointing sleeve respectively. Thus, for example in an application where PCMCIA interface is realized in a computer, each data line of the data bus of the computer is connected to one of the contact pins of the PCMCIA interface. Additionally, at least a part of the address and control lines are connected to the connector.
The connection between power supply of the electronic device and the PCMCIA interface is not defined in PCMCIA standard, wherein many alternative implementations exist in electronic devices. A battery is normally used as a power supply of portable electronic data processors. Typically, an application specific integrated circuit (ASIC) is used to control the current supply to the PCMCIA interface. Many types of current supply circuits, such as regulators and voltage converters, can be used between the battery and contact pins, the type of the current supply circuit being affected by the architecture of the electronic device and the internal operating voltage.
The PCMCIA cards have a size of a credit card (85.6 mm.times.54 mm), but the thickness of the cards can be 3.3 mm (type I), 5.0 mm (type II) or 10.5 mm (type III). Electrically the PCMCIA cards are connected to the electronic device as 8/16 bit I/O interface or memory. According to the PCMCIA standard, the PCMCIA card will have a memory area which can be read by an electronic device. This memory area includes information to identify the card. This information is called a card information structure (CIS) database. The card information structure includes tuples whereby every tuple includes definite information. Table 1 describes a CIS database tuple 1 which, in this case, includes information about the manufacturer of the card. The first field of the tuple, which is situated in address 0, informs the type of the tuple (=CISTPL_MANFID). The following field (situated in address 2) informs the link to the next tuple. The contents of this field can be used for designating the end of this tuple and the beginning of the next tuple. The value 4H (Hexadecimal) in the example of Table 1 informs that the number of information fields in this tuple is four.
TABLE 1 Byte Value Description 00 20H CISTPL_MANFID 02 04H Link to the next tuple 04 xxH Manufacturer ID (LSB) 06 yyH Manufacturer ID (MSB) 08 xxH Manufacturer identification (LSB) 0AH yyH Manufacturer identification (MSB) 0CH xxH Beginning of the next tuple
The power supply of the interface cards connected to the connector is normally implemented so that one or more operating voltages required for the card are connected from the electronic device via the connector. Thereby there will normally be no separate voltage sources used in the cards. This is a useful solution if the power consumption of the card is low. In practical embodiments, the maximum intensity of current that can be led to the card via contact pins is defined. This value may be different in different types of cards. For example, the maximum intensity of current allowed for each contact pin of said PCMCIA interface is about 0.5 A according to the PCMCIA standard. However, the PCMCIA standard does not define the maximum intensity of current of a PCMCIA card accurately. In practical embodiments, the upper limit of the intensity of current is about 1.0 A, because in connection with the PCMCIA cards usually two pins are used in the supply of each operating voltage. According to the PCMCIA standard, it is further recommended that the maximum intensity of current of the PCMCIA card during the start up of the apparatus should be limited to about 100 mA. Problems may arise with cards having a power consumption such that the current of the operating voltage pin exceeds the maximum allowable value or is close to this value. Temporary exceedings may not necessarily cause any damage but they can, however, shorten the operating life of the connector. Another drawback is that the power consumption of the card increases the power consumption of the electronic device, this being partly caused by the internal resistance of electronic device in the current supply circuit of the operating voltage pins.
When connecting a PCMCIA card to a (powered) electronic device, it reads the information included in a CIS database stored in the PCMCIA card. The connecting of the card can be detected for example in the following way. The card grounds by card sense lines CD1', CD2'the card detect pins CD1, CD2 in the connector, wherein an interrupt signal is generated to the processor of the electronic device. This will initiate the processor to run an interrupt service program including the necessary steps, such as to switch on the voltages to the card and to read the CIS database. FIG. 1 illustrates one PCMCIA interface in an electronic device as a reduced block diagram.
The operating voltage is supplied to the PCMCIA card via two operating voltage pins of the PCMCIA interface: V.sub.cc1, V.sub.cc2. According to the card version used, the operating voltage can be advantageously 3.3 V, 5.0 V or it can be selected to be either 3.3 V or 5.0 V. In case the voltage can be selected, the selection is controlled by data of the CIS database. Further, the PCMCIA interface has two programming voltage pins V.sub.pp1, V.sub.pp2 which are used only for programming of FLASH memory cards in known PCMCIA connections. These pins can advantageously be set at either 0 V, 12 V or at an operating voltage V.sub.cc, according to the data of the CIS database.
The voltage which is directed to the operating voltage pins V.sub.cc1, V.sub.cc2 is regulated, whereby power loss is effected in the regulator. The degree of the power loss is affected e.g. by the difference between the input and output voltages of the regulator and also by the current consumed by the PCMCIA card which is connected to the PCMCIA interface in the operating voltage pins V.sub.cc1, V.sub.cc2. The greater the resistance between the power supply and the operating voltage pins V.sub.cc1, V.sub.cc2 of the PCMCIA interface, the greater the power consumption and the voltage loss in the electronic device when the power consumption of the PCMCIA card is high.
In the following, it is described the data transmission from a PC by a mobile phone connected by an expansion card to a known expansion card connector of the PC, as is presented in FIG. 2a. FIG. 2b illustrates the operational blocks of the expansion card which can be connected to the expansion card connector of the PC and the operational blocks of the transmitter/receiver unit of the mobile phone. The operational blocks also illustrate the functional details of the units. The block 21 of the expansion card includes the standard interface whereby the connection to the PC is provided. The block 22 of the expansion card is an automatic calling module interpreting the commands, such as AT and V.25bis commands, i.e., so-called modem commands, sent from the PC to the card. The actual data, such as a facsimile transmission, is led from the connection block 21 to the adaptation and network service module 23 which converts the output data to the protocol required by the network service used. The data in the correct protocol form is led via a bus connection 24 to a fast serial bus.
The data coming via the serial bus enters a bus interface block 28 in a mobile phone. The bus interface block 28 directs the data according to the address information included in the data, either to a signalling and control block 26 or to a channel coder of the phone. The signalling and control block 26 is, in practice, the microprocessor of the phone. The channel coder of the phone is a digital signal processor DSP. The data is readily provided in a form that it can be directly led to the input/output port of the processors, wherein no conversions need to be made. The channel coder in block 25 codes both the control data from the block 26 and the traffic message from an external bus, such as a fax-message, whereby the coded information will be sent to the radio path via a radio unit 27.
When the data is coming from the radio path to the terminal, the process is completely understood by the explanation above. The data received from the radio path is decoded in a decoder 25. The decoded data is directed as control data or traffic data as such to the bus interface block 26 which adapts the data to the external bus. In the adapter, the functional steps are made in reverse order compared to the data transmission of the terminal explained above.
In particular, in connection with portable data processors (PC), mobile station adaptations have been designed, in which at least the transmitter/receiver unit TX/RX of the mobile station is provided in the PCMCIA standard card form. FIG. 3 illustrates a reduced block diagram of a transmitter/receiver unit of one mobile station positioned in a prior art PCMCIA card. The unit controlling the operation of the card is advantageously a microcontroller 13a (MCU) having e.g. a processor, memory (RAM, ROM), and input/output lines for connecting the microprocessor to the other electronics of the card. In addition, external memory 10 can be connected to the microcontroller 13a.
A transmitter TX comprises e.g. a modulator for modulating the signal to be sent, filters in particular for attenuating spurious emissions, a mixer in which the modulated signal is mixed to the local oscillator frequency for creating a radio frequency signal, and a power amplifier for amplifying the signal to be sent. The amplified signal is directed to an antenna ANT, which is connected to the card e.g. by means of a cable. A receiver RX comprises e.g. filters for filtering the received signals, a mixer for changing the radio frequency signal to be received to an intermediate frequency or, in a direct-change type receiver, to a baseband, and a detector for demodulating the received signal. Furthermore, the card has connection circuits, such as a control circuit 13b (ASIC), for transferring of signals between the PC and the transmitter/receiver. The transmitter/receiver unit has no power supply of its own, but the power supply is provided from the PC via the PCMCIA connection.
The watch-dog circuit RESET of the expansion card keeps the microcontoller 13a of the card at the initial phase of the operating voltage if the operating voltage of the card is, for some reason, insufficient. Thus, malfunctions of the microcontroller are eliminated e.g. during the coupling of the voltages.
Power consumption of the transmitter/receiver card varies during the operation. The power amplifier of the transmitter consumes a lot of power, wherein the power consumption is particularly high during the transmission. Since the card obtains the required operating voltage from the PC via the PCMCIA interface, the high power consumption causes the fact that the maximum current limit of the voltage pins is exceeded. The connector may be damaged, in case the PC or the card has no current restriction for hindering the exceeding of the current limit. On the other hand, the restriction of the current also restricts the initial power of the power amplifier, i.e., the intensity of the signal to be sent to the radio path. This may result in deterioration of the connection quality or even interruption of the connection.
A high power consumption also includes the disadvantage that power losses in the current supply circuit of the PC increase, wherein a part of the power taken from the power supply of the PC turns into heat inside the PC, and, on the other hand, the operation time of the PC at a single charge decreases, because the battery is run down faster.